# US 7,612,319 B2 · Method and apparatus providing a microlens for an image sensor

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- Number: US 7,612,319 B2
- Document ID: US7612319B2
- Status: Granted
- Kind: B2
- Application number: 11/449,756
- Filed: 2006-06-09
- Published: 2007-12-13
- Granted: 2009-11-03
- Earliest claimed: 2006-06-09
- Assignees: Aptina Imaging Corporation
- Inventors: Jiutao Li; Jin Li
- Web page: https://patentgrep.com/patent/US7612319B2

## CPC

- H10F 39/8063: {Microlenses}
- H10F 39/8053: {Colour filters}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

A microlens having a plurality of lens material units separated by a plurality of trenches and a method of forming the same is disclosed. The relationship of the trenches to the lens material is such that an average index of refraction of the microlens decreases from a center to an edge of the microlens.

## Claims

### Claim 1

A microlens structure comprising:
a microlens provided above a pixel, the microlens comprising a lens material unit comprising a plurality of separated blocks arranged in rows and columns separated by a plurality of trenches, wherein the lens material unit has a substantially flat upper surface.

### Claim 2 (depends on 1)

The structure of claim 1, wherein the plurality of trenches have varying cross-sectional widths from a center to an edge of the microlens.

### Claim 3 (depends on 1)

The structure of claim 1, wherein the plurality of trenches have varying cross-sectional widths increasing from a center to an edge of the microlens.

### Claim 4 (depends on 3)

The structure of claim 3, wherein blocks of the lens material unit have varying cross-sectional widths decreasing from a center to an edge of the microlens.

### Claim 5 (depends on 3)

The structure of claim 3, wherein cross-sectional widths of blocks of the lens material remain constant from a center to an edge of the microlens.

### Claim 6 (depends on 1)

The structure of claim 1, wherein the microlens has a substantially square shape.

### Claim 7

An image sensor comprising:
a pixel array comprising a plurality of pixels, each having a photosensor;
a microlens array formed over the pixel array, the microlens array comprising a plurality of microlenses with a substantially flat upper surface, each microlens comprising a lens material unit comprising a plurality of separated blocks arranged in rows and columns separated by a plurality of trenches; and
a fill material filling the trenches;
wherein an index of refraction of the fill material and an index of refraction of the lens material unit of an associated microlens introduce an average refractive index reduction from a center to an edge of an associated microlens.

### Claim 8 (depends on 7)

The image sensor of claim 7, wherein the fill material is air.

### Claim 9 (depends on 7)

The image sensor of claim 7, wherein the plurality of trenches have varying cross-sectional widths increasing from a center to an edge of an associated microlens.

### Claim 10 (depends on 9)

The image sensor of claim 9, wherein cross-sectional widths of blocks of the lens material unit decrease in a direction from a center towards an edge of the associated microlens.

### Claim 11 (depends on 9)

The image sensor of claim 9, wherein cross-sectional widths of blocks of the lens material unit remain substantially the same width in a direction from a center towards an edge of the associated microlens.

### Claim 12 (depends on 9)

The image sensor of claim 9, wherein cross-sectional widths of blocks of the lens material unit remain constant from a center to an edge of the associated microlens.

### Claim 13 (depends on 9)

The image sensor of claim 9, wherein blocks of the lens material unit have varying cross-sectional widths decreasing from a center to an edge of the associated microlens.

### Claim 14

A pixel array comprising:
a plurality of pixels; and
an array of microlenses over the plurality of pixels, each microlens having a substantially flat upper surface and an average refractive index reduction from a center to an edge of an associated microlens, wherein each microlens comprises a lens material unit comprising a plurality of separated blocks arranged in rows and columns separated by a plurality of trenches.

### Claim 15 (depends on 14)

The pixel array of claim 14, wherein cross-sectional widths of blocks of the lens material unit decrease while cross-sectional widths of the trenches increase in a direction from a center to an edge of an associated microlens.

### Claim 16 (depends on 14)

The pixel array of claim 14, wherein cross-sectional widths of blocks of the lens material unit remains substantially the same while cross-sectional widths of the trenches increases in a direction from a center to an edge of an associated microlens.

### Claim 17 (depends on 14)

The pixel array of claim 14, wherein an index of refraction of air and an index of refraction of the lens material unit of an associated microlens introduce the average refractive index reduction.

### Claim 18

A camera system comprising:
a processor; and
an imager connected to the processor and comprising:
a substrate having a plurality of pixels formed thereon, each pixel having a photosensor; and
a microlens array formed above the pixels and comprising a plurality of microlenses, each microlens including a lens material unit, each lens material unit comprising a plurality of separated blocks arranged in rows and columns separated by a plurality of trenches, wherein the lens material unit has a substantially flat upper surface;
wherein from a center to an edge of at least one of the microlenses a cross-sectional width of a trench is greater than a cross-sectional width of a previous trench;
wherein from the center to the edge of the at least one of the microlenses a cross-sectional width of a block of the lens material unit is smaller than a cross-sectional width of a previous block of the lens material unit.

### Claim 19

A method of fabricating a microlens array comprising: applying a microlens material over a pixel array; and
patterning the microlens material to form a set of microlenses having at least one microlens comprising a lens material unit comprising a plurality of separated blocks arranged in rows and columns separated by a plurality of trenches, wherein the patterning step further comprises patterning the microlens material to form a set of microlenses having a substantially flat upper surface.

### Claim 20 (depends on 19)

The method of claim 19, wherein the plurality of trenches having differing cross-sectional widths.

### Claim 21 (depends on 19)

The method of claim 19, wherein blocks of the lens material unit have differing cross-sectional widths.

### Claim 22 (depends on 19)

The method of claim 19, wherein the plurality of trenches have cross-sectional widths increasing from a center to an edge of the at least one microlens.

### Claim 23 (depends on 22)

The method of claim 22, wherein blocks of the lens material unit have cross-sectional widths decreasing from a center to an edge of the at least one microlens.

### Claim 24 (depends on 22)

The method of claim 22, wherein blocks of the lens material units have cross-sectional widths which remain constant from a center to an edge of the at least one microlens.

### Claim 25 (depends on 19)

The method of claim 19, wherein the plurality of trenches have cross-sectional widths increasing from a center to an edge of the at least one microlens while blocks of the lens material unit have cross-sectional widths which remain constant from the center to the edge of the at least one microlens.

### Claim 26 (depends on 19)

The method of claim 19, wherein the plurality of trenches have cross-sectional widths increasing from a center to an edge of the at least one microlens while blocks of the lens material unit have cross-sectional widths decreasing from the center to the edge of the at least one microlens.

### Claim 27 (depends on 19)

The method of claim 19, wherein the microlens material comprises photoresist material.

### Claim 28 (depends on 19)

The method of claim 19, wherein the microlens material comprises any inorganic material that can be patterned.

### Claim 29 (depends on 19)

The method of claim 19, wherein each microlens has a substantially square top down shape.

### Claim 30

A method of forming an image sensor comprising:
forming a pixel array comprising a plurality of pixels in a substrate, each pixel having a photosensor;
forming a microlens array having a substantially flat upper surface and comprising a plurality of microlenses, each microlens having a lens material unit comprising a plurality of separated blocks arranged in rows and columns separated by a plurality of trenches, each microlens being positioned above at least one pixel of the pixel array; and
filling the trenches with a fill material;
wherein the cross-sectional widths of the trenches increase in the direction starting from a focal point of the photosensor towards an edge of an associated microlens, the focal point being aligned with a center of the associated microlens.

### Claim 31 (depends on 30)

The method of claim 30, wherein the cross-sectional widths of blocks of the lens material unit decrease in a direction from a center to an edge of a microlens.

### Claim 32 (depends on 30)

The method of claim 30, wherein the cross-sectional widths of blocks of the lens material unit remain constant in a direction from a center to an edge of a microlens.

### Claim 33 (depends on 30)

The method of claim 30, wherein the fill material is air and the refractive index of air in relation to the refractive index of the microlens material introduces an average refractive index reduction in a direction from the center to the edge of the microlens.

### Claim 34 (depends on 30)

The method of claim 30, wherein the act of forming a microlens array comprises forming a plurality of flat upper surface for the microlenses.

### Claim 35 (depends on 30)

The method of claim 30, wherein the fill material is air.